Adding macros to push pinning roots - port PR #43 (#71)

Port #43 to dev. Add _NO_TPIN macros for pushing GC frames.

Author: qinsoon

src/interpreter.c

@@ -52,7 +52,14 @@ extern void JL_GC_ENABLEFRAME(interpreter_state*) JL_NOTSAFEPOINT;
 
 #else
 
+#ifdef MMTK_GC
+#define JL_GC_ENCODE_PUSHFRAME(n)  ((((size_t)(n))<<3)|2)
+// For roots that are not transitively pinned
+#define JL_GC_ENCODE_PUSHFRAME_NO_TPIN(n)  ((((size_t)(n))<<3)|6)
+#else
 #define JL_GC_ENCODE_PUSHFRAME(n)  ((((size_t)(n))<<2)|2)
+#define JL_GC_ENCODE_PUSHFRAME_NO_TPIN(n)  JL_GC_ENCODE_PUSHFRAME(n)
+#endif
 
 #define JL_GC_PUSHFRAME(frame,locals,n)                                             \
   JL_CPPALLOCA(frame, sizeof(*frame)+(((n)+3)*sizeof(jl_value_t*)));                \

src/julia.h

@@ -1053,8 +1053,41 @@ struct _jl_gcframe_t {
 
 #define jl_pgcstack (jl_current_task->gcstack)
 
+#ifndef MMTK_GC
 #define JL_GC_ENCODE_PUSHARGS(n)   (((size_t)(n))<<2)
 #define JL_GC_ENCODE_PUSH(n)       ((((size_t)(n))<<2)|1)
+#define JL_GC_DECODE_NROOTS(n)     (n >> 2)
+
+#define JL_GC_ENCODE_PUSHARGS_NO_TPIN(n)  JL_GC_ENCODE_PUSHARGS(n)
+#define JL_GC_ENCODE_PUSH_NO_TPIN(n)      JL_GC_ENCODE_PUSH(n)
+#else
+
+// We use an extra bit (100) in the nroots value from the frame to indicate that the roots
+// in the frame are/are not transitively pinning.
+// There are currently 3 macros that encode passing nroots to the gcframe
+// and they use the two lowest bits to encode information about what is in the frame (as below).
+// To support the distinction between transtively pinning roots and non transitively pinning roots
+// on the stack, we take another bit from nroots to encode information about whether or not to
+// transitively pin the roots in the frame.
+//
+// So the ones that transitively pin look like:
+// #define JL_GC_ENCODE_PUSHARGS(n)   (((size_t)(n))<<3)
+// #define JL_GC_ENCODE_PUSH(n)       ((((size_t)(n))<<3)|1)
+// #define JL_GC_ENCODE_PUSHFRAME(n)  ((((size_t)(n))<<3)|2)
+// and the ones that do not look like:
+// #define JL_GC_ENCODE_PUSHARGS_NO_TPIN(n)   (((size_t)(n))<<3|4)
+// #define JL_GC_ENCODE_PUSH_NO_TPIN(n)       ((((size_t)(n))<<3)|5)
+// #define JL_GC_ENCODE_PUSHFRAME_NO_TPIN(n)  ((((size_t)(n))<<3)|6)
+
+// these are transitively pinning
+#define JL_GC_ENCODE_PUSHARGS(n)   (((size_t)(n))<<3)
+#define JL_GC_ENCODE_PUSH(n)       ((((size_t)(n))<<3)|1)
+#define JL_GC_DECODE_NROOTS(n)     (n >> 3)
+
+// these only pin the root object itself
+#define JL_GC_ENCODE_PUSHARGS_NO_TPIN(n)   (((size_t)(n))<<3|4)
+#define JL_GC_ENCODE_PUSH_NO_TPIN(n)       ((((size_t)(n))<<3)|5)
+#endif
 
 #ifdef __clang_gcanalyzer__
 

src/subtype.c

@@ -274,7 +274,7 @@ static void re_save_env(jl_stenv_t *e, jl_savedenv_t *se, int root)
         }
         else {
             roots = se->roots;
-            nroots = se->gcframe.nroots >> 2;
+            nroots = JL_GC_DECODE_NROOTS(se->gcframe.nroots);
         }
     }
     jl_varbinding_t *v = e->vars;
@@ -367,7 +367,7 @@ static void restore_env(jl_stenv_t *e, jl_savedenv_t *se, int root) JL_NOTSAFEPO
         }
         else {
             roots = se->roots;
-            nroots = se->gcframe.nroots >> 2;
+            nroots = JL_GC_DECODE_NROOTS(se->gcframe.nroots);
         }
     }
     jl_varbinding_t *v = e->vars;
@@ -4146,7 +4146,7 @@ static int merge_env(jl_stenv_t *e, jl_savedenv_t *me, jl_savedenv_t *se, int co
     else {
         saved = se->roots;
         merged = me->roots;
-        nroots = se->gcframe.nroots >> 2;
+        nroots = JL_GC_DECODE_NROOTS(se->gcframe.nroots);
     }
     assert(nroots == current_env_length(e) * 3);
     assert(nroots % 3 == 0);